Lawinenlagebericht

Southeast Mountains

Crested Butte Avalanche Center
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Lawinengefahr

Thu
Hochgebirge
3 · Erheblich
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
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Kernpunkte

Storm totals approaching a foot with moderate winds have created dangerous conditions on wind-loaded slopes.  In steep, leeward terrain, it will be easy to trigger an avalanche involving the recent snow.  In wind-affected terrain, there is also a lingering threat that you can trigger a larger avalanche that breaks on old, weak snow.  The safest riding is in wind-sheltered terrain today, where you'll have to manage for shallow storm instabilities.   

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–2

    Up to 10" of storm snow and transportable winds at higher elevations have formed sensitive drifts in leeward terrain.  You will easily trigger soft slabs in cross-loaded gullies, below ridges, or in other terrain features that catch drifting snow.  Winds have shifted from the west to the south to the east with this storm, forming slabs on most aspects and in some terrain that is typically wind scoured.  Avoid steep slopes where you find more than a foot of thicker, denser-feeling snow.   Cracking in the snow is a sign of instability.  

    An example of a wind slab from earlier this year.  

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1.5–2.5

    Several large avalanches last week broke on faceted weak layers in the lower snowpack (Hunter Hill, Snowmass).  Recent persistent slab activity has been rare and most problematic on wind-drifted slopes at higher elevations.  Be cautious of similar terrain where wind drifting has formed dense slabs of varying thicknesses.  This loading event could make persistent slabs more reactive today.  

Avalanche Discussion

Northwest Mountains:  The Northwest Mountains got walloped by over a foot of snow last night, with 1" per hour rates since yesterday afternoon. Storm totals are now 18" to 24" and will increase more today.  That's a significant load that is expected to create widespread storm instabilities, both soft slabs and sluffs, breaking within the storm snow and at the storm interface.  Observations yesterday indicated that the new snow was not bonding well to the storm interface, which is a mix of crusts, faceted crusts, and near-surface facets. The bottom line is there is a lot of snow that will start moving on you in steep terrain.  Choose conservative terrain.  

Southeast Mountains:  The storm didn't do as well near and east of Crested Butte, with weather stations showing about 3" to 5" of snow overnight, and storm totals up to 10".  The biggest hazard is on wind-drifted slopes, where slabs will be larger and most sensitive.  Winds have evolved from west to south to east throughout the storm, so expect to find drifted slabs on most aspects and in some atypical locations.  In wind-protected terrain, expect to manage sluffing within the new snow, and in a few areas, thin soft slabs.  Conditions are most dangerous at higher elevations or along the boundary of the Northwest Mountains.   We've bumped the likelihood of persistent slabs up to possible today with the concern that the additional loading could make suspect wind-drifted slopes a bit more reactive than earlier this week.  Unusual east winds this morning will be drifting onto slopes with the shallowest and weakest snowpacks which don't often see loading.    

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